Method and system for determining bilirubin concentration

Abstract

A system and method embodying the invention can be used to detect a characteristic or condition of a patient. A method embodying the invention may include the steps of illuminating a portion of a skin of the patient with light, detecting a frequency spectrum of light scattered from the skin, determining, from first and second portions of the spectrum, a first parameter indicative of a blood content of the skin and a second parameter indicative of a melanin content of the skin, determining, from a third portion of the spectrum, a third parameter indicative of an uncorrected bilirubin concentration, and calculating a corrected bilirubin concentration based on the first, second and third parameters.

Description

RELATED APPLICATIONS[0001]This application is a continuation of U.S. patent application Ser. No. 09 / 589,403, filed Jun. 8, 2000 now abandoned, which is a continuation-in-part of U.S. patent application Ser. No. 09 / 286,649, filed on Apr. 6, 1999 now U.S. Pat. No. 6,192,734, which is in turn a continuation of U.S. patent application Ser. No. 09 / 054,490, filed on Apr. 3, 1998 now U.S. Pat. No. 5,924,981, which is in turn a continuation-in-part of U.S. patent application Ser. No. 08 / 904,766, filed on Aug. 1, 1997 now U.S. Pat. No. 6,045,502, which is in turn a continuation-in-part of U.S. patent application Ser. No. 08 / 621,182, filed Mar. 21, 1996 now abandoned, which in turn is a continuation-in-part of U.S. patent application Ser. No. 08 / 587,949, filed on Jan. 17, 1996 now U.S. Pat. No. 5,860,421. The contents of these applications are hereby incorporated by reference.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]This invention relates to instruments that require cal...

AI Technical Summary

Benefits of technology

[0024]An object of the invention is to provide a simple and accurate apparatus and method of measuring a patient's bilirubin concentration.

[0025]A measurement instrument embodying the invention, that utilizes electromagnetic radiation, may include one or more transmit and receive fiber optic waveguides for directing electromagnetic radiation to a material or tissue to be measured and for conducting reflected or dispersed radiation back to a sensor of the instrument. The instrument may be configured such that radiation transmitted from the instrument toward the material or tissue being measured is directed toward the material or tissue at an angle relative to a plane normal to the surface of the material or tissue so as to reduce backscattering effects.

[0027]Another feature of the invention is that a measurement instrument designed to measure a bilirubin concentration in a patient may accomplish the measurement using the amplitude of radiation reflected from a patient's skin at first and second wavelengths representing a blood content of the skin, and at a third wavelength representing an uncorrected bilirubin concentration. Such an instrument may also utilize the amplitude of reflected radiation at fourth and fifth wavelengths that represent a melanin content of the patient's skin.

Problems solved by technology

Although others have proposed calibration fixtures that compensate for these variations in instrument performance, none have provided a simultaneous solution to both the calibration issue and the problems associated with the spread of infection in a medical setting.

Furthermore, calibration devices that are designed to be reused can become damaged by sunlight, temperature, humidity and other effects, which could lead to errors in calibration.

However, neither of these approaches involves an inexpensive calibration target that can be easily discarded after each use.

In addition, neither of these systems prevent a user from taking a measurement without going through a calibration step.

This approach, however, is neither simple nor inexpensive.

Again, however, this approach does not involve an inexpensive, disposable calibration device.

However, the boot is not present during the measurement and there is no provision to prevent reuse of the boot.

Newborn infants and prematurely born infants are particularly susceptible to hyperbilirubinemia.

Often this is due to the lack of functioning glucoronyl transferase enzyme in their liver, or excessive red blood cell breakdown associated with erythroblastosis fetalis.

Of course, this invasive approach requires that blood be drawn to perform the test.

Unfortunately, these devices have failed to give satisfactory correlations when used over a heterogeneous population.

Since patient populations are rarely homogeneous, transcutaneous bilirubin measuring methods have not been widely accepted clinically.

That approach, however, has not been approved for use in the United States, although it is used for screening purposes in some U.S. institutions.

In addition, that approach does not account for variations in skin color and thickness.

This approach does not have a quantitative accuracy required to have a high correlation to serum bilirubin.

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